All I can tell you is my story. I went through 18 months of daily contact on an almost 50/50 shared care basis. This was the first 18 months of separation. My ex insisted on daily contact with the children and I had no clue I could object. When the children were with him, I would phone and he would refuse to pick up the phone. I would have to phone back several times and he would then pick up the phone but I don't think he picked up first time once during that time. If I didn't phone (because I was at work late and travelling or just wanted a night off from his crap), he would phone me in front of the children and leave messages about what a bad mother I was. By contrast, the expectation was that I picked up by the second ring and if I didn't, he would scream at me that I was a 'contact-blocker' and 'wasn't acting in the children's best interests' and a whole host of personal and unpleasant stuff. It got to the point where I was sitting on the sofa with the phone in my hand at least 15 minutes before he was due to phone with tears pouring I was so....well, I guess I was scared.
It took 18 months to find the guts to tell him to sod off. He hasn't phoned since. Typical bully - just needed standing up to. The downside is that I can no longer phone the children when they are with him but I think it is less unsettling for all of us to do it this way.
Whilst I wouldn't suggest everyone is like my ex, it is intrusive and there needs to be some kind of compromise. I would be happy for him to phone every day as long as he accepted that if I don't answer, it's not because I'm being difficult, it's about the fact that I'm doing something else, we're not in, or we're just enjoying being together and don't want disturbing and not because I am deliberately being difficult.